WASHINGTON, April 15 (UPI) -- A cow with obvious signs of a brain disease appeared in a slaughterhouse in upstate New York in August 1997, generating concerns about mad cow disease because it initially tested positive for the deadly disorder.

Recent media reports have suggested there were procedural problems with testing the cow and that it might have been possible the animal was infected with the mad cow pathogen -- also known as bovine spongiform encephalopathy or BSE.

The initial test turned out to be invalid, however, and the U.S. Department of Agriculture tested the animal multiple times, finding nothing to indicate the cow was infected with BSE and ultimately ruling it negative, a two-year investigation by United Press International has revealed.

USDA officials have denied assertions the cow was not properly tested and pointed out the testing records show the cows were tested multiple times and found to be negative.

In mid-August 1997, USDA veterinarian Masuo Doi inspected a 2-year-old cow at the Oriskany Falls Packing plant in Oriskany Falls, N.Y. The young cow was unable to stand and showed other symptoms that made it a candidate for BSE testing.

Another suspicious cow had been delivered to the plant just three months earlier. It also initially was suspected of being infected with BSE. Doi said a USDA laboratory pathologist, who initially looked at brain tissue from that cow, suspected the animal was infected, but subsequent testing at a different USDA lab came back negative.

The events of that earlier case had left Doi skeptical about the USDA's testing procedures, however, so when the suspicious cow appeared just a few months later, he secretly obtained a sample of the cerebrospinal fluid from the animal and sent it by FedEx to Joe Gibbs, head of the National Institutes of Health's Laboratory for Central Nervous System Studies in Bethesda, Md. -- a now-defunct lab that conducted groundbreaking work on mad cow and similar disorders in humans.

"We didn't distrust the USDA lab on the first case ... but by this time we did," said Doi, who worked for USDA's Food Safety and Inspection Service for nearly 30 years before retiring in December. "That's why we took our own sample."

The inspectors also videotaped the animal and UPI was shown the tape. It shows a cow lying down with its right eye pointing up. The animal did not respond to rapid hand motion in front of its eye or having its nose or ears tapped with a stick. The cow would not drink water and its hind legs seemed paralyzed. It also could not stand up.

Doi said new information discovered about the May case by UPI persuaded him that the cow was negative for BSE. He still wonders what type of disorder afflicted the August cow, but said it did not appear to be BSE.

In response to recent media accounts that have implied he was suggesting mad cow cases have been covered up by the USDA, Doi said, "I don't think you have enough to say that BSE is being covered up in the United States."

Gibbs, who died in 2001, said the cerebrospinal-fluid test came back positive. However, Michael Hansen, a biologist with the Consumers Union, told UPI that Gibbs later informed him the CSF sample was contaminated with blood -- which would cause the test to turn positive, whether the cow was infected with mad cow disease or not.

An entry in a logbook kept by Gibbs, in which the CSF sample was noted, was obtained by UPI. In that entry, the sample is described as "bloody."

Gibbs decided to look into the issue anyway and contacted Linda Detwiler, a veterinarian and head of the USDA's BSE surveillance program at the time. Gibbs knew Detwiler and asked her if the cow had been tested for BSE by the USDA.

Detwiler confirmed to UPI that Gibbs had called her and informed her of the positive CSF result, but she said the result was a false positive, because the sample was obtained after the animal died and it contained blood.

Michael Harrington, a scientist with the Huntington Medical Research Institute in Pasadena, Calif., told UPI that both conditions -- blood contamination and being obtained after death -- would cause the CSF test to produce a positive whether or not the animal was infected with mad cow. The problem with blood in the sample is the CSF test detects a protein called 14-3-3 that can be an indication of brain damage, but the protein also is found in blood.

Harrington, who helped develop the CSF test, said the problem with a sample taken after death is it "would always be positive in my experience and there would be no way to distinguish it from any disease."

The cow in question already had undergone one type of mad cow test at the USDA, a test called immunohistochemistry. This came back negative for any signs of BSE.

Detwiler said in response to the phone call from Gibbs that she asked the USDA lab to pull the sample from the animal and retest it using another test called Western blot. This test also failed to find any evidence of BSE.

Detwiler's account is confirmed in USDA testing records obtained by UPI through the Freedom of Information Act.

A report in USDA's testing records notes that a histopathological examination -- a rudimentary test considered unreliable for excluding mad cow cases -- was "of questionable validity because it is unknown whether" the tissue being examined included the obex region.

The report went on to state the examination "revealed no combination of lesions which is consistent with ... bovine spongiform encephalopathy."

Based on all the evidence in the case, the USDA officials at the lab concluded, "No evidence of infection by any agent which is known to cause a transmissible spongiform encephalopathy was found."

Elizabeth Mumford, a veterinarian and BSE expert at Safe Food Solutions in Bern, Switzerland, a company that provides advice on reducing mad cow risk to industry and governments, reviewed the records of the case for UPI and said, " I think actually they did a good job."

Mumford said her colleagues in Switzerland had also looked at the documents and they agreed there was nothing to indicate this cow might have been positive.

"There's no alarm bells ringing over on this side of pond," she said.

Detwiler, who is now retired from the USDA but still is respected by BSE experts and has a reputation for being forthright, told UPI, "I didn't have any doubt then or now that it wasn't BSE."